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Abstract:

The Faroe Islands are located in the North Atlantic between Shetland and Iceland. The population of 48,000 mainly relies on seafood, and traditional diets also include meat and blubber from the pilot whale. The meat is contaminated with methylmercury and the blubber with lipophilic pollutants, mainly PCB and DDE. From 1985, prospective studies have been carried out to characterize the adverse effects of seafood contaminants.

In the design of these studies, decisions were made in regard to the types of biologic samples to collect for contaminant analyses (as exposure biomarkers). Beneficial parameters such as essential nutrients and of breast-feeding were also recorded. Follow up for developmental patterns, especially in regard to neurobehavioral and immunologic outcomes, was carried out at carefully selected ages that were deemed optimal for the main effect parameters.

Cohort 1: A cohort of 1022 singleton births was assembled in the Faroes during a 21-month period of 1986–1987. The methylmercury exposure was assessed by analysis of cord blood, cord tissue, and maternal hair. The mercury concentrations covered a span of approximately 1000-fold. The first detailed examination (neuropsychologic, neurophysiological, and neuropediatric) took place at age 7 years, ie, just before school entry. A total of 917 of the eligible children (90.3%) completed the examinations. The children were reexamined at age 14 with a similar participation rate. Postnatal exposures were assessed only in connection with these examinations and averaged approximately one fifth of the prenatal levels. Clear dose–response relationships were observed for deficits in attention, language, and memory and in neurophysiological parameters. Postnatal exposure was not associated with these outcomes.

Cohort 2: The next cohort was established during a 12-month period in 1994–1995 and included 182 singleton term births from consecutive births with emphasis of high-exposure communities. Maternal serum from the last antenatal examination and milk were also collected in this case with the purpose of analyzing PCB and related pollutants. These children were examined by the Neurologic Optimality Score at age 2 weeks and again by a variety of tests at approximately 1-year intervals. Examinations at age 10 years have just been completed. Mercury-associated deficits were again found, most clearly at age 2 weeks and at school age.

Cohort 3: This cohort consists of 650 children born during 1998–2000. After a 2-week examination, a subgroup was seen at age 18 months to ascertain antibody responses to childhood immunizations. A comprehensive examination was then carried out just before and one month after the 5-year vaccination. These children are now being reexamined at age 7 years with emphasis also on neurobehavioral function. Mercury exposures have declined in this community, and emphasis is now on lower-level mercury neurotoxicity and the independent effects of PCBs and related substances.